Editing techniques are known in which the normal sequence of video frames from a video clip is altered to produce a re-timed sequence. For example a clip having a duration of only a few seconds may be repeated or individual frames of a clip may be removed to reduce slightly the duration of the clip. These techniques are often employed to synchronise video to an audio soundtrack and in more sophisticated applications for example to synchronise the movements of a mouth (possibly that of an animal) to a recorded soundtrack, of say, speech. The legs of an animal may also be synchronised in this way so that a single leg movement may be repeated many times to create, say, the illusion of a cow `dancing` in time to recorded music.
A machine which has made these effects, and many more, available to commercial video producers is manufactured by the present Applicant and sold under the trademark "HARRY". In this machine, frames of video are digitally encoded and stored on magnetic discs, as disclosed in U.S. Pat. No. 4,688,106 assigned to the present applicant. A problem with known techniques for stretching video clips is that each stretching (or compressing) process has been limited to very simple functions, such as stretch by 20%, or remove 3 frames etc. Thus, a complicated movement lasting only a few seconds may have to be built up from many small clips having different functions applied thereto.